It appears this won't work anymore for the new output generated by kindlegen v2.3.
I've been poking around with it (comparing code from the latest mobi_unpack), but I'm slow as molasses—plus I'm not really grasping exactly how to stitch the mobi back together minus the source section (but I can find the source section ).

Also, I was wondering if anyone else thinks it makes sense to have an option to strip (and save to a separate file) the old-mobi portion from the new mobi-KF8 hybrid? I still use kindlegen for my own personal use and won't always want the extra bulk of the additional KF8 data (especially when transferring to a device that can't make use of it).